These days, it is fashionable among science writers to claim that the difference between humans and other animals is one of degree. Well, here’s one clear-cut difference: only human beings are aware of what other individuals can see, while guide dogs appear to be blissfully unaware that their owners cannot see.
A 2008 study by the French anthropologist Florence Gaunet, titled, “How do guide dogs of blind owners and pet dogs of sighted owners (Canis familiaris) ask their owners for food?” (Animal Cognition, July 2008, 11(3):475-83) was the subject of a recent blog article in Discover magazine (Seriously Science, July 1, 2014). The design of the experiment was simplicity itself: Dr. Gaunet reasoned that if guide dogs understood that their owners were blind, then when they are prevented from accessing food that they were able to access previously, they should be less likely to gaze at the container where the food used to be stored and then at their owners’ faces, than dogs belonging to sighted owners. Instead, guide dogs should try to get their owners’ attention by resorting to non-visual cues. Surprisingly, however, Dr. Gaunet found that although some guide dogs did use auditory cues (such as licking their lips noisily) to get their owners’ attention when they were hungry, they were no less likely to use visual cues than dogs belonging to sighted owners. She concluded that while guide dogs were capable of learning new ways of getting their owners’ attention, they do not understand that their owner cannot see them. Here’s the abstract of her paper:
Although there are some indications that dogs (Canis familiaris) use the eyes of humans as a cue during human-dog interactions, the exact conditions under which this holds true are unclear. Analysing whether the interactive modalities of guide dogs and pet dogs differ when they interact with their blind, and sighted owners, respectively, is one way to tackle this problem; more specifically, it allows examining the effect of the visual status of the owner. The interactive behaviours of dogs were recorded when the dogs were prevented from accessing food that they had previously learned to access. A novel audible behaviour was observed: dogs licked their mouths sonorously. Data analyses showed that the guide dogs performed this behaviour longer and more frequently than the pet dogs; seven of the nine guide dogs and two of the nine pet dogs displayed this behaviour. However, gazing at the container where the food was and gazing at the owner (with or without sonorous mouth licking), gaze alternation between the container and the owner, vocalisation and contact with the owner did not differ between groups. Together, the results suggest that there is no overall distinction between guide and pet dogs in exploratory, learning and motivational behaviours and in their understanding of their owner’s attentional state, i.e. guide dogs do not understand that their owner cannot see (them). However, results show that guide dogs are subject to incidental learning and suggest that they supplemented their way to trigger their owners’ attention with a new distal cue.
Canine cognition researcher Clive Wynne claims to have come up with a case of a dog that knew its owner was blind and even used this knowledge to its own advantage. Professor Wynne described the case in a message he sent to animal researcher Professor Hal Hertzog (“Professor, Does My Dog Know I’m Blind?”, Psychology Today, December 5, 2010):
Hal, I was recently told a story by a dog trainer that is relevant to Leo’s question. [Leo was a caller on talkback radio who asked Professor Hertzog on air if he thought his dog knew he was blind – VJT.] She had “inherited” a dog from a blind lady who passed on to her. Soon after acquiring the dog, the trainer came downstairs to the kitchen. She was not terribly surprised to see the dog on the kitchen counter helping itself to some food that had been left out. What surprised her was that the dog, on hearing her footsteps on the stairs, did nothing to jump down. Instead the dog continued to eat! It was accustomed to the idea that just because a human was in the room, that did not mean that the human could detect her presence on the forbidden kitchen counter. This dog clearly knew what it meant for a human to be blind.
On the contrary, I would say that the case demonstrates precisely the reverse: clearly, the dog did not know what it meant for another human being to see. If it had known that, it would have jumped off the counter with alacrity when it heard its new owner’s footsteps on the stairs. The dog’s ability to take advantage of its former owner’s blindness was simply the product of conditioning: after years of not being punished by its owner for being in the kitchen, it finally lost its fear of helping itself to food that it found there.
In his article, Professor Hertzog mentions another suggestion, made by ASPA science advisor Steve Zawistowski, that whether dogs know their owners are blind might depend on whether the owner lost their sight suddenly or gradually. Once again, I would argue that if the dog possessed a “theory of mind” and was able to understood that its field of vision was different from its owner’s, then it should have been able to grasp the fact that its owner could not see, almost immediately. If it was able to adjust to a gradual loss of sight on the part of its owner but not a sudden one, that would indicate that its adjustment was due to conditioning, rather than an understanding of the fact that its owner can no longer see.
Canine ethologist Professor Stanley Coren, F.R.S.C., has argued that because dogs turn to their owners for advice by looking at their faces when confronted with a novel problem they have to solve, this indicates that dogs do have a “theory of mind.” But another expert, Ádám Miklósi, has pointed out that wolves, which are dogs’ closest relatives, don’t do this. It is hardly likely that dogs have a “theory of mind” while wolves don’t. What is more likely is that dogs have slowly evolved to interact visually and vocally with human beings, over the last 30,000 years. That’s why they often to their owners for advice when they need assistance.
What about the mirror test?
A baby exploring his reflection. Image courtesy of roseoftimothywoods and Wikipedia.
I should also mention that dogs, like most animals, do not recognize themselves in mirrors, even after repeated exposure to mirrors. Instead, they treat the image they see in a mirror as if it were another individual, as can be seen from this video. This is strong prima facie evidence that they lack self-awareness – and by implication, awareness of other individuals’ mental states. By contrast, as early as 18 months, half of all children recognize the reflection in the mirror as their own (Lewis, M. and Brooks-Gunn, J., Social cognition and the acquisition of self, New York: Plenum Press, 1979, p. 296). Very few animals are capable of passing the mirror test: humans, great apes, magpies, a very small number of Asian elephants, and possibly bottlenose dolphins, although researcher Gordon G. Gallup, who first developed the test in 1970, is doubtful. In any case, philosopher Michael P. T. Leahy maintains that mirror tests fail to demonstrate self-awareness in animals. In his provocative book, Against Liberation (Routledge, revised paperback edition, 1994), he remarks that all these tests show is that “the creatures recognise their own bodies” (p. 146). However, “for self-consciousness to get a foothold it would be necessary to show that they were aware of recognising themselves; which is awareness of a different order.”
Only humans can see the world from another individual’s perspective
Researchers Derek C. Penn and Daniel J. Povinelli have concluded that the ability to see the world from another individual’s perspective appears to be confined to human beings, and there is no good evidence that chimpanzees or any other non-human animals possess it:
The available evidence suggests that chimpanzees, corvids and all other non-human animals only form representations and reason about observable features, relations and states of affairs from their own cognitive perspective. We know of no evidence that non-human animals are capable of representing or reasoning about unobservable features, relations, causes or states of affairs or of construing information from the cognitive perspective of another agent. Thus, positing an fToM [folk theory of mind – VJT], even in the case of corvids, is simply unwarranted by the available evidence… (Penn and Povinelli, On the lack of evidence that non-human animals possess anything remotely resembling a ‘theory of mind’, Philosophical Transactions of the Royal Society B, 29 April 2007, vol. 362 no. 1480, pp. 731-744. See p. 737 for quote.)
In their 2007 paper, Penn and Povinelli proposed two carefully controlled experiments which could provide evidence of a “theory of mind” in non-human animals. Even adult chimpanzees who were used to interacting with human beings failed the first experiment (referred to in the paper as the opaque visor experiment and described on pages 737-739) proposed by the authors, whereas 18-month-old human infants passed the same test in flying colors. So much for the claim that chimps are as smart as three-year-old children.
Summing up the current state of animal cognition research, Penn and Povinelli conclude in their 2009 paper, On Becoming Approximately Rational: The Relational Reinterpretation hypothesis by Derek C. Penn and Daniel J. Povinelli (in S. Watanabe, A. P. Blaisdell, L. Huber and A. P. Young (eds.), Rational animals, irrational humans, Tokyo: Keio University Press, 2009, pp. 23-44):
…[A]lthough there is abundant evidence that apes and monkeys act as if they are taking the visual perspective of others into account (e.g., Flombaum & Santos, 2005; Hare et al., 2006), there is no evidence that they are actually representing or reasoning about others’ subjective visual experience as distinct from the observable behavioral cues causally related to others’ actions in the world (Penn & Povinelli, in press). Nor is there any evidence that nonhuman primates understand that others have a subjective visual experience analogous to their own (Povinelli et al., 2000).
All of the evidence collected to date suggests that chimpanzees only represent others’ goals and intentions in terms of external states of the environment and observable behavioral cues but do not understand that others have internal mental representations of goals and unobservable intentions which causally guide others’ behavior (cf. Tomasello et al., 2005). (Penn and Povinelli, 2009, PDF, pp. 17-18)
Regarding the alleged ability of some birds belonging to the crow family (corvids) to attribute mental states to other individuals, Penn and Povinelli argue that a more parsimonious interpretation of the evidence makes more sense:
In all of the experiments with corvids cited above, it suffices for the birds to associate specific competitors with specific cache sites and to reason in terms of the information they have observed from their own cognitive perspective: e.g. ‘Re-cache food if a competitor has oriented towards it in the past’, ‘Attempt to pilfer food if the competitor who cached it is not present’, ‘Try to re-cache food in a site different from the one where it was cached when the competitor was present’, etc. The additional claim that the birds adopt these strategies because they understand that ‘The competitor knows where the food is located’ does no additional explanatory or cognitive work. (Penn and Povinelli, 2007, p. 6)
Penn, Holyoak and Povinelli conclude that while corvids are highly remarkable birds, there is no evidence that they are aware of each others’ mental states:
The best evidence for a ToM [theory of mind] system in a non-primate comes from the work of Emery, Clayton and colleagues (Emery & Clayton 2001; 2004b; in press)…. Results such as these leave no doubt that corvids are remarkably intelligent creatures, able to keep track of the social context of specific past events, as well as the what, when, and where information associated with those events (Clayton et al. 2001). But nothing in the results reported to date suggests that corvids actually reason about their conspecifics’ mental states – or even understand that their conspecifics have mental states at all – as distinct from their conspecifics’ past and occurrent behaviors and the subjects’ own knowledge of past and current states of affairs (Penn & Povinelli 2007b; Povinelli et al. 2000; Povinelli & Vonk 2003; 2004). (Penn, Holyoak and Povinelli, 2008, p. 120)
In recent years, it has also been alleged that apes, corvids and chickadees possess the ability to plan for the future. I discussed and critically evaluated the evidence to date in my post, Do apes plan for the future? Why I’m skeptical (October 23, 2013).
In short: the evidence to date points to the existence of a profound qualitative difference between the mental abilities of human beings and other animals. What this suggests is that people really are in a moral and psychological category of their own, after all.
(Note: the image of a yellow labrador retriver dog at the top of this post is courtesy of user Elf and Wikipedia.)